#if条件判定语句
if 1<2:
    print('hello')

#if多路分支
if 1>2:
    pass
elif 2>3:
    pirnt(1)
else:
    print(2)

#try,except防止出错后停止执行
try:
    print(hello)
except NameError:
    print('hello')

if 1<2:
    print('hello')


#任务实现：等级划分

while(True):
    try:
        score=input('请输入考试成绩:')
        score=float(score)
        if score>=90:
            print('A')
        elif 80<=score<90:
            print('B')
        elif 70<=score<80:
            print('C')
        elif 60<=score<70:
            print('D')
        else:
            print('不合格')
    except:
        print('输入的成绩是非字符型的！')




